This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. These studies are investigating the safety of suppressing expression of the gene that causes Huntington's disease in the normal rhesus macaque putamen as well as the therapeutic efficacy of decreasing the expression of this gene in a rhesus model of Huntington's disease. To date, we have shown efficacy of reducing HTT expression in the rhesus macaque putamen by 45%. This suppression of HTT is not associated with the manifestation of any behavioral abnormalities nor neuropathological changes in the putamen.